The spread of illicit drugs, such as narcotics and stimulants, has been a global problem. In many countries including Japan, illicit drugs having effects similar to stimulants or cannabis (such drugs are generally called “dangerous drugs” in Japan) are regulated individually (i.e. for each compound). In recent years, a wide variety of analogue compounds produced by partially altering the backbone chemical structures of existing drugs or by replacing their functional groups with different ones have been circulating one after another, making it difficult to regulate every individual compound. To deal with such a situation, a so-called comprehensive regulation, which is aimed at regulating compounds by their main skeletons rather than regulating individual illicit drugs, has been put into effect in some countries and regions, such as Japan, the UK and some of the states in the United States.
In general, identification of such illicit drugs or poisons has been performed using a gas chromatograph mass spectrometer (GC-MS) or liquid chromatograph mass spectrometer (LC-MS). Specifically, this is normally achieved as follows: A mass spectrum obtained by a measurement of a target sample using a GC-MS or LC-MS is compared with mass spectra obtained by measurements of known kinds of standard samples or mass spectra contained in a commonly available database, so as to search for a compound having a spectrum pattern identical or similar to that of the obtained mass spectrum and thereby identify the compound detected in the target sample (for example, see Non Patent Literature 1).
However, in many cases, it is difficult to obtain a standard sample for a newly circulated illicit drug produced by the aforementioned partial alteration of a chemical structure. Furthermore, mass spectra corresponding to such drugs are not contained in any existing databases, while at the same time it is not easy to create a database which completely contains mass spectra of a large number of compounds subject to the comprehensive regulation. Therefore, it is considerably difficult to identify all the illicit drugs subject to the comprehensive regulation or estimate their structures, by the aforementioned conventional method which uses a GC-MS or LC-MS.
For example, the comprehensive schedule prepared under the Pharmaceutical Affairs Act in Japan (see Non Patent Literature 2) contains a list of compounds which have the main skeleton consisting of 2-amino-1-phenyl-propane-1-one (commonly called “cathinone”) as being subject to the comprehensive regulation. The list shows 495 kinds of cathinone-based compounds which differ from each other in the kinds of functional groups bonded to three sites on this main skeleton. FIG. 3 shows the chemical structure of cathinone-based compounds. As will be detailed later, R1 is either hydrogen (H) or one of six kinds of substituent groups, thus providing seven choices. R2 is either occupied by one of two kinds of substituent groups or unoccupied by any substituent group, thus providing three choices. R3 is either occupied by one of eight kinds of substituent groups (with a total of 23 patterns having different bonding sites) or unoccupied by any substituent group, thus providing 24 choices.
For such a large number of cathinone-based compounds, the conventional method of identifying compounds by the pattern matching of mass spectra cannot be used to identify the compounds or estimate their structures unless those compounds are individually registered in a database.
In GC-MS, an electron ionization (EI) method is widely used as the ionization method. However, when the EI method is used for a cathinone-based compound, there will be almost no molecular ion detectable on the obtained mass spectrum. The amount of fragment information will also be small, since the thereby detected fragment ions are only the ions produced by α-fragmentation of amine. Therefore, even if the target compound to be identified is registered in a database, it is difficult to accurately distinguish this target compound from phenethylamine-based compounds, whose mass-spectrum patterns are similar to those of the cathinone-based compounds. Such a high degree of similarity to the phenethylamine-based compounds makes it even more difficult to identify the cathinone-based compounds.
To deal with such a problem, an attempt of structural estimation has been made in which the result of an analysis using a GC-MS is combined with high-precision mass information obtained using a nuclear magnetic resonance (NMR) apparatus, liquid chromatograph time-of-flight mass spectrometer (LC-TOFMS) or similar device. However, this method requires preparing a plurality of devices, each of which is expensive. Furthermore, a highly experienced operator is needed to conduct measurements and analyze data.